1. Field of the Invention
The present invention relates to an optical apparatus provided with a signal generator.
2. Related Background Art
A lens barrel has recently been provided with a position detector for electrically detecting the position of a moving barrel so that the information about the position of the moving barrel, which is electrically detected by the position detector, is input to an information processor and used for various controls according to demand.
FIG. 4 is a longitudinally sectional view of a lens barrel of the type that is generally known. In the drawing, reference numeral 1 denotes a mount having a claw portion 1a for connecting the mount 1 to a camera body, and reference numeral 2 denotes a fixed barrel connected to the mount 1 and having a guide groove 2a parallel with the optical axis. Reference numeral 3 denotes a zoom ring rotatably supported by the fixed barrel 2 and comprising an outer barrel portion 3a and an inner barrel portion 3b having a cam groove 3c. Reference numeral 4 denotes a helicoid ring having a cam groove 4a with which a roller 5 provided on the zoom ring 3 is engaged, a helicoid 4b which is provided on the outer periphery thereof and a guide groove 4c which is provided on the inner periphery thereof and with which a straight key 6 provided on the fixed barrel 2 is engaged. Reference numeral 7 denotes a front group lens barrel having a lens group L1 and a helicoid 7a which is provided on the inner periphery thereof and in which the helicoid 4b of the helicoid ring 4 is screwed. Reference numeral 8 denotes a rear group lens barrel having a lens group L2 and a roller 9 which is provided on the outer periphery thereof and which is engaged with the guide groove 2a of the fixed barrel 2 and the cam groove 3c of the zoom ring 3. Reference numeral 10 denotes a contact member provided on the mount 1 so as to serve as an electrical contact with the camera body and connected, by soldering, to a ring-shaped circuit substrate 11 on which electrical parts are loaded to form an electrical circuit. Reference numeral 12 denotes a flexible printed board having one end which is connected to the circuit board 11 by soldering and the other end which is bonded to the fixed barrel 2, as well as having a position detecting Gray code pattern provided thereon. On the other hand, a brush 13 which slidably contacts with the Gray code pattern of the flexible printed board 12 is provided on the outer barrel portion 3a of the zoom ring 3 corresponding to a notched portion of the inner barrel portion 3b of the zoom ring 3. Reference numeral 14 denotes a rubber ring wound around the outer periphery of the zoom ring 3 so as to improve zooming operation properties.
The operation of the above-described arrangement is described below.
Magnification can be changed by rotating the zoom ring 3 around the optical axis. During this operation, the rear group lens barrel 8 having the lens group L2 is moved along the cam locus of the cam groove 3c of the zoom ring 3 in the direction of the optical axis because the roller 9 is movably supported by the guide groove 2a of the fixed barrel 2 only in the direction of the optical axis. At the same time, the male helicoid ring 4 is moved by the roller 5 in the direction of the optical axis opposite to the cam locus of the cam groove 4a because the helicoid ring 4 is supported so that the straight key 6 fixed to the fixed barrel 2 can be moved in the guide groove 4c only in the direction of the optical axis. At this time since relative movement is produced between the male helicoid ring 4 and the front group lens barrel 7, the lens group L1 is moved along the locus opposite to the cam groove 4a, like the male helicoid ring 4. As described above, the magnification is changed by rotating the zoom ring 3 around the optical axis so as to move the lens groups L1, L2 in the direction of the optical axis.
In addition, the focusing operation can be carried out by applying force in the rotational direction to the front group lens barrel 7 so as to move the front group lens barrel 7 having the lens group L1 in the direction of the optical axis while rotating it by employing the screw relation between the helicoid 4b and the helicoid 7a.
In this conventional example, a position detector comprises the brush 13, the flexible printed board 12 and part of the circuit formed on the circuit substrate 11. Namely, since the brush 13 is slidably moved on the Gray code pattern on the flexible printed board 12 as the zoom ring 3 is rotated, the instantaneous position of the brush 13 is electrically detected by the detection circuit on the circuit substrate 11 so that the position of the zoom ring 3, i.e., the focal distance in the lens system, can be detected.
However, in the above conventional example, the need for the flexible printed board 12 having the position detecting Gray code pattern causes an increase in the cost and the need for troublesome works of positioning the flexible printed board 12 when the flexible printed board 12 is bonded to the fixed barrel 2 and connecting the flexible printed board 12 to the circuit substrate 11.
In addition, the need for a space on the outer periphery of the fixed barrel 2 to which the flexible printed board 12 is bonded significantly affects other designs such as the position of the guide groove 2a, the formation of the cam groove 3c in the zoom ring and the like. This leads to deterioration in optical characteristics.